The Kern Canyon Fault (Late-Quaternary Active Kern Canyon Fault) is a dextral strike-slip fault (horizontal) that runs roughly around 150 km (93 mi) beside the

Kern River Canyon The Kern River Canyon is a canyon in Kern County, California. It is located in the Southern Sierra Nevada. The canyon was formed by the Kern River and connects the Kern River Valley and southern San Joaquin Valley The San Joaquin Valley ...

through the mountainous area of the Southern

Sierra Nevada Batholith The Sierra Nevada Batholith is a large batholith that is approximately 400 miles long and 60-80 miles wide which forms the core of the Sierra Nevada mountain range in California, exposed at the surface as granite. The batholith is composed of ...

. The fault was a

reverse fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic f ...

in the Early Cretaceous epoch during the primal stages of the Farallon plate

subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

beneath the North American Continental Plate and fully transitioned into a strike-slip

shear zone In geology, a shear zone is a thin zone within the Earth's crust or upper mantle that has been strongly deformed, due to the walls of rock on either side of the zone slipping past each other. In the upper crust, where rock is brittle, the shear ...

during the Late Cretaceous. Professor Robert W. Webb of the University of Chicago was the first to research the fault in 1936; He found a lava flow (Pliocene age) that covered the northern end of the fault trace where the Little Kern and Kern River coincided. Without any evidence of deformation affecting the hardened lava and without any evidence found previously when investigating the fault line, Webb deemed the fault to be inactive. In 2007, Professor Elisabeth Nadin (University of Alaska Fairbanks) discovered that while mapping the faults within the Southern Sierra Nevada, there had been several accounts of activity along the Kern Canyon Fault well into the Quaternary Era. Her research continued into 2010, which explicitly entailed the lines of evidence that overturn the proposition that the fault was inactive for more than 3.5 million years.

Fault Zones

The Three Sub-Divisions

Due to the continued activity of the fault as well as its extension, the Kern Canyon Fault is sub-divided into three different zones; The proto-Kern Canyon Fault Zone, the Kern Canyon Fault Zone, and the late Quaternary active Kern Canyon Fault.

Proto-Kern Canyon Fault Zone

The proto-Kern Canyon Zone is an old

ductile Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...

shear zone found at the northern segment of the fault line. Evidence of mylonitized zones, 90 Ma intrusive rocks, and Mesozoic-metamorphic rocks mention that this was where the Kern Canyon Fault (which shares these same rock specimens) first emerged and had drifted away from due to the constant activity within the batholith. Nadin exhumed the shear zone and recovered that it extended from the northern end of Harrison Pass, CA to the south-eastern arm of Lake Isabella, CA.

The Kern Canyon Fault Zone

The Kern Canyon Fault Zone is a north-striking feature that harbored pre-Quaternary crustal deformation such as right-lateral strike slip and east-down normal displacement. These episodes caused bedrock displacement along the fault line, allowing the fault itself to dip steeply. It extends from Walker Basin, CA to Harrison Pass and coincides with the proto-Kern Canyon Fault Zone starting from Kernville to Harrison Pass.

The Late-Quaternary Active "Kern Canyon Fault"

The late-Quaternary active Kern Canyon Fault extends the ~150 km (99) miles from Walker Basin past Harrison Pass. Its existence exploits both the Proto-Kern and Kern Canyon Fault Zones' weaknesses, resulting in ruptures along the zones over the past 15 thousand years.

Fault Geology

The Kern Canyon fault, according to the early study of Webb, is made up of 90 percent of granodiorite (a phaneritic-textured intrusive igneous rock similar to granite) and although densely covered by soils and brush, Webb discovered traces of sheared breccias and mylonites in specific zones along the fault. While conducting a study of the fault's capability of supporting Isabella Dams, Treaser (1948) recorded in-depth analysis of the fault's basement rocks. His method of understanding the geology of the fault included surface study, drilling and trenching; using this approach, he was able to discern the rocks affected by this fault zone at 800 feet in width (244m). These specimens include quartzite, olivine, gabbro, sheared granitic rocks, metasedimentary rocks, and diorite.

References

{{California Faults Seismic faults of California Sierra Nevada (United States) Geology of Kern County, California Geology of Tulare County, California Kern River Kern River Valley Natural history of Kern County, California Natural history of Tulare County, California Sequoia National Park